B.C. Braces for the Big One

Seismologists are tracking a series of tremors that started in Puget Sound

If you live in BC's south coast area, you are being advised to check your emergency supplies, first aid kits and flashlights because there is an increased probability of a major earthquake hitting the coast during the next week.

Seismologists at the Geological Survey of Canada, based at the Pacific Geoscience Centre in Sidney, B.C., have been tracking a series of tremors that started in Puget Sound along the U.S. West Coast three days ago. The tremors are slowly working their way up Vancouver Island.

The low-level shaking that is only picked up by sensitive equipment installed up the coast, rumbled through southern Vancouver Island beginning on Thursday, said seismologist Garry Rogers. "It's like a giant tear that moves 15 to 20 kilometres a day," he said.

The tremors are caused by a tear in the bottom plate of the Cascadia fault. In 2003, Pacific Geoscience Centre scientists discovered that the tremor activity occurs every 14 months and so, can be accurately forecasted.

"Vancouver Island, the edge of the continent, is usually storing up energy like a giant spring. Vancouver Island is usually moving towards Ottawa and now it is moving towards Japan," Rogers said.

The directional change of the "sticking and slipping" will carry on for about another week. The plates will then go back to normal.

"For some reason, the bottom portion fails every 14 months. It sticks for 14 months and slips for a week or two, right under Vancouver Island," Rogers said.

People are wondering how much extra stress these episodes add to the plates, and how much closer it brings B.C. to the "big one."

"What it is doing is adding straws to the camel's back, and one of these straws is going to break the camel's back. Right now, we're in the process of adding a humongous straw, and we don't know how many more we need to break the camel's back," Rogers said.

The next window of high earthquake risk will be duing April 2008.

Isn't this fascinating. I had no idea that this happened, almost like clockwork, every fourteen months.